Hydrocarbon oils are widely used as base oils for cosmetic raw materials, fiber lubricants, food additives, mechanical lubricating oils, release agents, defoamers, inter alia. Hydrocarbon oils are characterized by low cost and excellent resistance to acid and alkali. On the other hand, the dimethylpolysiloxane oils, which are used in the very same applications as the hydrocarbon oils, are characterized by low surface tension and excellent resistance to heat and cold. However, the dimethylpolysiloxane oils are expensive, and this has limited their use to a narrower range of applications.
Investigations have been made into base oils prepared by blending dimethylpolysiloxane oil into a hydrocarbon oil. However, these two components are inherently incompatible and separate from each other as time elapses after their mixing.
Numerous methods have already been proposed in order to solve this problem. Thus, for example, Japanese Patent Application Laid Open Number Sho 62-124193 teaches the blending of alkyl-modified polysiloxane oil into mineral oil as a method for preparing a lubricating oil suitable for application as a refrigerant. Japanese Patent Application Laid Open Numbers Hei 1-153792 and Hei 1-95193 teach the blending of fluoroalkyl-functional polysiloxane oil into mineral oil as a method for preparing a lubricating oil suitable for reducing the friction at the rubbing zones of plastic substrates.
There are, however, limitations on the use of the former lubricating oil--which contains alkyl-modified polysiloxane oil--because it does not invariably give a good lubricating performance. The latter lubricating oils--which contain fluoroalkyl-modified polysiloxane--suffer from a poor lubricating performance and an expensive polysiloxane component.